1.1 C √ (1) 1.2 B √ (1) 1.3 D √ (1) 1.4 D √ (1) 1.5 A √ (1) 1.6 C √ (1) 1.7 D √ (1) 1.8 D √ (1) 1.9 B √ (1) 1.10 D √ (1) 1.11 D √ (1) 1.12 C √ (1) 1.13 B √ (1) 1.14 B √ (1) 1.15 A √ (1) 1.16 C √ (1) 1.17 A √ (1) 1.18 C √ (1) 1.19 D √ (1) 1.20 B √ (1)
[20]
QUESTION 2: SAFETY
2.1 Safety – Centre lathe
Look out for revolving work pieces √
Do not remove shavings by hand √
Be careful not to run the cutting tool into the chuck √
Do not make any adjustments on the work piece while the machine is running √
Do not leave tools on the machine while in operation √ (Any 2 x 1) (2)
2.2 Safety – Tensile Tester
Use safety goggles √
Do not apply excessive pressure √
Test piece to be well secured for testing √
Check hydraulic fluid level √ (Any 2 x 1) (2)
2.3 Safety – Spring Tester
Spring tester should be in a good condition √
Spring tester must be fitted correctly and firmly √
Ensure that the spring cannot slip out of position before applying the load √
An uniform load must be applied √
Release the load carefully and uniformly √ (Any 2 x 1) (2)
2.4 Safety – Cylinder Leakage
Clean the area around the spark plug, before removing the spark plug √
To prevent dirt from falling into the cylinder. √
Be careful when removing radiator cap √
The water may be hot and under pressure. √
Do not exceed the specified pressure to test the cylinder √
To prevent damage to the seals and tester. √
The tester must fit properly and be well tightened in the spark hole or injector hole √
To prevent damage to the tester and spark hole or injector hole. √ Any 2 x 2 (4)
[10]
QUESTION 3: TOOLS AND EQUIPMENT
3.1 Compression testing
3.1.1
Wet compression test √
Dry compression test √ (2)
3.1.2
Worn cylinders √
Worn piston rings √
Worn piston √
Leaking inlet valve √
Leaking exhaust valve √
Leaking cylinder head gasket √ (Any 2 x 1) (2)
3.2 Oil pump
Oil pressure meter or oil pressure tester √ (1)
3.3 Cooling system test
Remove the radiator cap and fit the tester √
Pump air at the prescribed pressure into the system √
Note the reading √ and if the reading drops, it indicates a leaking system √
To test for a leaking cylinder-head gasket, √ the engine is started. √
If the reading increases while the engine idles, it indicates on a leaking cylinder-head gasket √ (7) [12]
QUESTION 4: MATERIALS
4.1 Iron-carbon properties
4.1.1 Pearlite:
Good ductility √
Hard √
Strong and tough √
Resistant to deformation √ (Any 2 x 1) (2)
4.1.2 Cementite:
Intensely hard √
Brittle. √ (2)
4.2 Critical points
4.2.1 AC1 – lower critical point
The lowest temperature to which steel must be heated to be hardened. √√
The lowest temperature where the structure starts to change. √√ (Any 1 x 2) (2)
4.2.2 AC3 – high critical point
The highest temperature to which the steel can be heated to obtain maximum hardness. √√
The temperature where the steel completely loses its magnetic properties. √√
The temperature where the steel's structure is at its finest. √√ (Any 1 x 2) (2)
4.3 Carbon content determines the hardness of steel. √ (1)
4.4 Cementite structure in steel determines the hardness. √ (1)
4.5 Ferrite structure in steel determines the ductility. √ (1)
4.6 Austenite is a solid solution of iron and carbon also called iron carbide. √ The structure is at its finest. √ (2) [13]
QUESTION 5: TERMINOLOGY
5.1 Gear calculation
5.2
5.3 Screw thread cutting
Set up the work piece in the lathe and turn the part to be threaded to the major diameter of the thread. √
Set the compound slide to the correct angle (30°) to the right and set the tool up accurately in the post. √
Consult the index plate of the quick-change gearbox for 2 mm pitch and move the levers accordingly. √
Start the lathe and set the cutting tool so that it just touches the work piece. Set graduated dials to zero (cross feed and compound slide) √
Move cutting tool a short distance off end of work piece and feed compound slide say 0,06 mm inwards. √
With lathe turning, engage half nuts at the correct line on the chasing dial, putting the first cut in progress. √
Withdraw the cutting tool quickly and disengage the half-nut lever. Return the carriage to the starting point of the thread. √ OR Stop the machine, leave half nut engaged, back off slide past zero and return carriage to start position in reverse √
Check with thread gauge to see if thread pitch is correct. √
Repeat with successive cuts until thread is complete. (Remember to bring cross-feed collar back to zero for each cut) √
Each successive cut is set by means of the compound slide. Check thread with ring gauge for correct fit. √
(10) [30]
QUESTION 6: JOINING METHODS
6.1 MIG/MAGS welding equipment
6.1.1 MIG/MAGS welding equipment √ (1)
6.1.2 Labels
A = Shielding gas cylinder √ B = Regulator √ C = Gas flow meter √ D = Continuous wire reel √ E = Welding gun √ F = Arc √ G = Earth clamp √ (7)
6.1.3 Purpose
Prevents oxygen √ to come in contact with the molten metal.√ (2)